(a) Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device. More particularly, the present invention relates to a method of forming a contact hole for electrically connecting an upper conductive layer to a lower conductive layer, where they are electrically insulated by an insulating layer.
(b) Description of the Related Art
As semiconductor integrated circuits have become more highly integrated, a width or a space of an interconnection line has become smaller, and a size of a contact hole or via hole to connect between metal interconnection line layers, or a size of a contact hole to connect a gate or a source/drain to a metal line layer, has also been decreased. Accordingly, much research has been conducted in order to decrease the contact resistance of such a contact hole and to improve a process window.
More particularly, multi-layer wiring technology is a technology to make interconnection lines in the integrated circuits multi-layered so as to highly integrate a semiconductor device in a limited area of a substrate. Therefore, such multi-layer wiring technology has a merit of decreasing the size of a semiconductor chip because there is no need to consider a space for interconnection lines to pass between semiconductor devices.
FIG. 1A to FIG. 1D are cross-sectional views showing sequential stages of a conventional method of forming a contact hole in a semiconductor device.
As shown in FIG. 1A, a first insulation layer 100 is formed on a substrate which includes a transistor (not shown) and multi-layer metal lines in its lower part. A first conductive layer 120 is formed on the first insulation layer 100. In addition, a second insulation layer 110 is formed on the first insulation layer 100 and the first conductive layer 120. Thereafter, a second conductive layer 130 is deposited on the second insulation layer 110, and is patterned by performing a photolithography and etching process.
Subsequently, as shown in FIG. 1B, a third insulation layer 140 is blanket deposited on the surface of the substrate, including the second conductive layer 130. A resist 150 is coated on the third insulation layer 140, and the resist 150 is patterned through a lithographic process by removing the resist 150 in a region where a contact hole (or via hole) will be formed.
As shown in FIG. 1C, a contact hole 141 and a contact hole 143 are formed by etching the third insulation layer 140 and the second insulation layer 110 using the patterned resist 150 as an etch layer. The contact hole 141 is a hole in which a contact to the second conductive layer 130 on the second insulation layer 110 is to be formed, and the contact hole 143 is a hole in which a contact to the first conductive layer 120 on the first insulation layer 100 is to be formed. Therefore, the etching depth of the contact hole 141 is different from that of the contact hole 143. Consequently, as shown in FIG. 1C, when the contact hole 141 and the contact hole 143 are simultaneously formed in the same etching process, etching for the region of the contact hole 143 may be performed correctly to a surface of the first conductive layer 120, but etching for the region of the contact hole 141 may be performed excessively such that the second conductive layer 130 may be damaged by overetching into an upper part of the second conductive layer 130.
On the other hand, as shown in FIG. 1D, etching for the region of the contact hole 141 may be performed correctly to a surface of the second conductive layer 130, but etching for the region of the contact hole 143 may be performed insufficiently such that the first conductive layer 120 may not be exposed. Therefore, when contact holes or via holes having different etching depths should be formed simultaneously, a deterioration of contact resistance or excessive damage to a conductive layer may occur because a process window is very insufficient in the case of a small-sized contact hole.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention. Therefore, it may contain information that does not form prior art or other information that is already known in this or any other country to a person of ordinary skill in the art.